This specification refers to bipolar semiconductor devices, in one embodiment to speed diodes and a manufacturing method therefor.
Diode structures are desired to have a very good surge current strength and also a sufficient dynamic robustness. Moreover, the losses occurring during operation are to be kept small. For this purpose, CAL diodes (CAL=Controlled Axial Lifetime) and EMCON diodes (EMCON=Emitter Controlled) have been developed. In the case of CAL diodes, a heavily doped p-type emitter is used. However, manufacturing of CAL diodes requires intensive helium irradiation and further methods for reducing the charge carrier lifetime in order that the turn-off losses do not become too high. EMCON diodes, by contrast, have a relatively weakly p-doped emitter. However, a reduced surge current strength is observed in this case.
A further diode variant is the “speed diode” (self-adjusted p-emitter efficiency diode). While the forward current of this diode flows via a weakly p-doped zone during normal operation, in the surge current case charge carriers are injected from highly p-doped zones and contribute to a high surge current strength and surge energy capacity, respectively. However, the dynamic robustness of the known speed diode is often unsatisfactory.
For these and other reasons there is a need for the present invention.